1. Field of the Invention
This invention relates to a technique of estimating the time of failure of a product including plural components and the degree of degradation of each component, and reflecting these to a maintenance plan.
2. Description of the Related Art
Conventional maintenance planning depends on the experience and intuition of individual servicemen. Therefore, the risk of damage to a user caused by the unavailability of a product and the maintenance cost cannot be balanced with each other.
That is, in order to reduce the risk of product failure, a replacement operation takes place more than necessary so as to replace a component in which failure is very likely to occur, before its service life end, and the maintenance cost increases. Conversely, to lower the maintenance cost by using up the component to the end of its service life, a visit is made after failure occurs. Therefore, it is a trade-off with a longer downtime and increased damage to the user caused by the unavailability of the product.
In another type of industry, there is an example of maintenance planning based on the cost and risk (see, JP-A-2004-152017). However, this is limited to a judgment on whether to conduct maintenance or not, based on the risk, and it is difficult to estimate the cost if the number of components to be replaced (consumable parts) increases. That is, when judging whether to replace consumable parts or not, a very high calculation cost is required for calculating which combination of consumable parts should be replaced as the best maintenance plan. Also, it cannot be seen how long the time for next visit can be prolonged, and the cost cannot be calculated simply.